My house sometimes gets small amounts of air in the lines because I am located at a high point in the water companies service. In most areas like mine, the water company will not do anything to correct this. If it is a major problem and you thing can cause damage to your equipment (plumming) you may have to take legal action.
If you are not at a high point of service, then your pipes are allowing air in somehow. However, we are only guessing without more information such as: * Public water or well water? * House located at top of hill, in valley, or on level area? * Do any of your neighbors experience this? * Do you have a water pressure regulator installed? * Do you have a water softener? * How much air over what amount of time?